Ever since humanity has been able to launch projectiles into space to take nosey pictures that make us all feel insignificant, a major priority has been to somehow communicate with any alien life forms that might come across this space detritus and wonder who shot a space probe right into their upper atmosphere. Using physics, mathematics, art, and even Earth's greatest weapon (Carl Sagan), our species has painstakingly crafted the first tentative social overtures towards the magnificent extraterrestrials we hope are listening.

This audio salute, one of the first radio signals intended specifically for interstellar intelligence, was meant as a test of the new Evpatoria Planetary Radar (EPR). In November 1962, the Unique Korenberg Telescope Array transmitted the greeting towards Venus, using simple Morse Code. Given the location of Venus in November 1962, the message is even now winging its way towards Libra.

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Message Content: The words "MIR," "LENIN," and "SSSR," in Morse.

Message Assumptions: The Morse message assumes that aliens will be listening for a message that brief. Also, given the specificity, we'll assume the content was symbolic; otherwise you're asking for quite a bit of Earth current-events context.

Likely Impression: You know when a kid draws all over the wall with crayon, and you'd be really annoyed except you notice that the kid's managed to spell his name somehow, so you end up mildly surprised, and after you send them to their room you talk about whether it's already time for preschool? Like that.

Mounted to Pioneer spacecraft before they made their merry way into the inhospitable reaches of space outside the solar system, the Pioneer Plaque was the first-but not the last!-interstellar communiqué in which Carl Sagan had a say. Attached to both Pioneers and positioned to minimize the corrosive effects of solar dust, the plaque might well be the first thing an alien culture knows about us. (Well, the plaque, and also the fact that we hurl things into space and aim them right at you.)

Message Content: The Pioneer plaque forewent an auditory component and instead tried to include the maximum information about Pioneer's source; thanks to Sagan, Linda Salzman Sagan, and Franke Drake, every inch is packed with data: A diagram of a hydrogen atom; a pulsar map with the sun at the center, showing the relative distances of 14 pulsars and the binary code of their periods, which can help date the launch era; figures of a nude man and woman set in front of a to scale silhouette of Pioneer; a sketch of our solar system with a long arrow indicating the Earth as the planet that launched the little guy.

Message Assumptions: Alien life form can see in two dimensions, has a concept of arrows.

Likely Impression: Earth is filled with humanoids who haven't had the brains to develop clothes, possibly because they're too busy fighting off the absolutely enormous serpent reaching out from the third planet and launching space probes willy-nilly.

Taking what they had learned from the Pioneer message and fine-tuning it, Frank Drake and Carl Sagan built a richer, stronger, mathier greeting card on the second go-round. The message was beamed out into space only once in 1974, aimed at the M13 star cluster, and consisted of 1679 digits (binary, naturally) that, when collected, formed a picture that gave a very Pong picture of our little blue planet.

Message Content: Quite a bit. The Arecibo message managed to pack in the numbers one through ten, the atomic numbers of the elements found in DNA, the formula for DNA, a DNA helix, the figure of a human with a binary scale, a diagram of the solar system, and a sketch of Arecibo.

Among the most poetic of humanity's letters to the universe, the Golden Record sent into space with each of the Voyager probes is more a symbol than a pointed communiqué-the spacecraft are so small that when they stop emitting radiation, they'll be almost impossible to detect in the vastness of space, especially as it's still a good 40,000 years away from the nearest star (AC+79 3888).

Message Content: The Sagan went to the drawing board for a third time to develop a richer tapestry of the Earth experience. The Golden Record contains 116 images, from the old pulsar-map and hydrogen-atom standbys to images of animals, plants and architecture; it also contains a multitude of sounds, from the sound of surf and birdsongs to musical compositions from around the world, and greetings in fifty-five languages. Also included is a cover that gives a quick pictorial explanation of how to play the record and read the images, and a cartridge, in case the aliens have already moved on to 8-track.

Message Assumptions: That aliens will ever find it.

Likely Impression: Earthlings are just a bunch of hopeful, lovin' fools

The Cosmic Call, broadcast from Evpatoria in 1999 and 2003 and sent to nine different stars, is perhaps our most serious attempt at a spacegoing message. With several messages and repetitions per broadcast, and the widest directional net, this might well be the message most likely to get us noticed.

Message Contents: The 1999 Cosmic Call contains the Dutil-Dumas Message (the "Interstellar Rosetta stone," built on a series of symbols), the Brastaad Message (which uses the mathematical language of the Dutil-Dumas Message to give more information on message sponsor Team Encounter), the Arecibo Message, and a staff message from Team Encounter. The 2003 edition substituted a Bilingual Image Glossary for the Braastad Message, showing concepts such as Family.

Message Assumptions: With a message this diverse, even if the specifics don't get through, aliens will definitely understand there's a civilization longing to make contact.

Likely Impression: That kid in the mall that sings two bars of a song over and over as loudly as it can, waiting for attention. Then it does the same thing in another language.

The children are our future-literally, in this case, as a group of Russian teens built their own message to space and beamed it to six stars in 2001. Along the same lines as the Cosmic Calls that preceded and followed it, the Teen Age Message also contained some innovative new twists.

Message Contents: The message contains data in three forms-radio signals, analog data (music), and binary digital information: The radio signals attempt to imitate transmission from the Sun itself; the "First Theremin Concert for Aliens" includes Russian folk songs and the finale of Beethoven's 9th Symphony, and the binary digital follow-up gives an Arecibo-esque rundown of basic mathematic and physical constants.

Message Assumptions: The uniquely-teen pressure of making the perfect mix tape.

Likely Impression: A return binary message, 100 years from now, asking for an interstellar envoy to teach them how to play the theremin.

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The chances of an alien civilization having the means, motive, and opportunity to catch any of these messages are slim; certainly it's not likely that humanity will last long enough to catch any return messages showing the atomic weight of silver and bizarre, monstrous forms that we realize only too late were actually pictures of aliens galloping on the back of the enormous monsters they ride into battle with all who contact them. Even if the aliens are friendly, perhaps it's just as well their chances of finding us are slim; all these messages, no matter their medium of context, are the equivalent of a first-date lie that paints humanity as a united, noble, peaceful civilization that cherishes their planet and wishes only to share their knowledge with others. Aliens that actually make it to our planet will have a long, awkward standoff while they look back and forth from the Voyager record to the planet, wondering what happened to the 24/7 beachside music festival they were promised.

On the other hand, if there's a chance that all they're looking for is theremin lessons, we might be okay! Related: everyone should start practicing the theremin immediately.

Genevieve Valentine's first novel, Mechanique: a Tale of the Circus Tresaulti, is forthcoming from Prime Books in May 2011. Her short fiction has appeared in or is forthcoming from: Running with the Pack, The Living Dead 2, The Way of the Wizard, Teeth, Clarkesworld, Strange Horizons, Fantasy, Lightspeed, Escape Pod, and more. Her appetite for bad movies is insatiable, a tragedy she tracks on her blog.

Lightspeedis an online magazine focusing exclusively on science fiction, where you can expect to see near-future, sociological soft sf, to far-future, star-spanning hard sf, and anything and everything in between.Lightspeed also features a variety of nonfiction features, fiction podcasts, and Q&As with our authors that go behind-the-scenes of their stories.